The invention relates to a deformable roof flashing material for use in connection with skylight windows and the like roof penetrating structures, said roof flashing material comprising a sandwich construction with two outer layers of metal foil and at least one intermediate non-adhesive layer positioned between the outer layers, in which the material at least in one direction has been given a continuous waveform.
Such deformable flashing materials are used for providing a water and snow tight connection between the roof penetrating building structure which may be a chimney, an air shaft, a skylight window or the like, and the surrounding roofing.
Particularly in connection with corrugated roofing, such as for instance tiles, whereby, during mounting, a considerable deformation of the flashing material is required, the use of flashing materials with built-in excess of material in the form of corrugations or foldings has been proposed as a replacement for the previously used sheet lead, which admittedly has a good deformability but the use of which on the other hand is connected with problems seen from an economic and environmental point of view.
Thus, the EP Patent No. 38 222 and the international published specification no. WO95/28536 disclose sandwich materials or composite materials, in which the surplus material has been provided by corrugation in waveform in one or two directions of the flashing material.
In the first-mentioned publication, the individual layers of the structure are kept together by means of an adhesive bitumen layer as the intermediate layer. Apart from the drawback, seen from an environmental point of view, that the individual components of the flashing material cannot be separated at the dismounting, the adhesive connection will have a negative influence on the deformability of the material, and it will in particular be difficult to obtain the lasting deformation necessary for obtaining the desired water and snow tightness.
In the latter publication the mutual securing between the layers forming part of the sandwich structure is established by a second corrugation in a direction substantially perpendicular to the first one. Even though this material has excellent properties in respect of deformability, the manufacturing process is on account of the second corrugation necessarily more costly, and simultaneously the number of intermediate layers and/or the thickness thereof is limited.
From German Utility Model publication no. G 87 01 605.2 a further flashing material is known which comprises a lead layer coated with aluminium foil which in view of mutually securing the layers is pleated and possibly provided with an edge folding. However, the pleating entails that the adaptation to the subjacent roofing is made difficult on account of the sharp foldings of the pleating, which foldings moreover serve as breaking direction for cracks and tear, which on the other hand entails the risk of rain penetrating to the subjacent roof construction.
On this background it is the object of the invention to provide a deformable roof flashing material of the type mentioned by way of introduction and comprising in undeformed condition a sandwich construction in which the layers are not displaced relative to one another and which is moreover easy to handle during the mounting without the risk that the layers of the sandwich constructions are displaced substantially relative to one another, which construction on the other hand, however, allows a certain relative movement of the layers and which is moreover easy and cheap in manufacture and at the same time meets the requirements to a sufficient surplus of material.
This object is met by a roof flashing material, which is characterized in that at least the intermediate layer/s adjacent to the outer layers is/are made from a resilient material, and in that said waveform is formed in such a manner that it maintains the mutual positioning between the outer layers and the adjacent intermediate layer/s by friction.
The special embodiment of waveform in combination with the resilient intermediate layer/layers causes an effective securing between the outer layers and the adjacent layers without the use of adhesive agents, which might prevent deformation of the material during adaptation to the surrounding roofing, and at the same time the single waveform establishes the desired surplus of material, the simplified manufacture and the freedom of choice in respect of the number of layers and/or the thickness thereof. Furthermore, the material has the advantage that it will be self-closing in case of cracks or ruptures.
In a preferred embodiment of the invention the waveform is made as a substantially harmonic sine curve, an optimal mechanic friction being obtained between the outer layers and the adjacent intermediate layer/layers which are at the same time allowed to remain undeformed during the working process.
Further advantageous embodiments of the invention are described in the remaining dependent claims.
The invention furthermore relates to a method for the manufacture of a flashing rail with a skirt made from the roof flashing material as stated in claim 12.